1. Technical Field
The present invention pertains to monitoring data transmission through communications systems. In particular, the present invention pertains to monitoring methods and apparatus for measuring and displaying peak throughput in data transmission systems to assess bandwidth utilization for an entire access channel or individual transmission circuits. The present invention is related to the system disclosed in U.S. Pat. No. 5,521,907 (Ennis, Jr. et al) the disclosure of which is incorporated herein by reference in its entirety.
2. Discussion of Prior Art
Communications systems, especially packetized data networks, are currently utilized in various applications for transmission and reception of data across varying distances. Packetized data networks (e.g., local and wide area networks) typically format data into packets for transmission to a particular site. In particular, the data is partitioned into separate packets at a transmission site wherein the packets usually include headers containing information relating to packet data and routing. The packets are transmitted to a destination site in accordance with any of several conventional protocols known in the art (e.g., Asynchronous Transfer Mode (ATM), Frame Relay, High Level Data Link Control (HDLC), X.25, etc.), by which the transmitted data are restored from various packets received at the destination site.
Packetized data communications are especially appealing for common carrier or time-shared switching systems since a packet transmission path or circuit is unavailable only during the time when a packet utilizes the circuit for transmission to the destination site, thereby permitting other users to utilize that same circuit when the circuit becomes available (i.e., during intervening periods between packet transmissions). The access channel (i.e., channel connecting a site to a communications system) and each individual transmission circuit typically have a maximum data carrying capacity or bandwidth expressed in units of bits per second (bits/second). The access channel utilization is typically measured as an aggregate of the individual circuit utilizations and has a fixed bandwidth, while the individual circuits may be utilized by several users wherein each user may utilize an allocated portion of the circuit bandwidth (e.g., the frame committed information rate (CIR)). In other words, the committed information rate is the amount of bandwidth guaranteed to the user for a data transmission circuit. When a user sends data on a circuit in excess of the circuit committed information rate, the additional data exceeding the rate might possibly be discarded during transmission, depending upon circuit traffic conditions, thereby requiring re-transmission and degrading performance. Since the cost of bandwidth is directly proportional to the bandwidth quantity, cost effective communications systems tend to utilize the minimum amount of bandwidth necessary to facilitate data communications.
In order to determine the proper bandwidth requirements for an access channel or specific circuit, it is desirable to monitor access channel and circuit activity and view the bandwidth utilization. Various prior art monitoring systems are available that measure traffic, throughput, load and other communications system characteristics. For example, U.S. Pat. No. 4,775,973 (Tomberlin et al) discloses a communications measurement matrix display for a protocol analyzer wherein the protocol analyzer measures, and the matrix display shows, communications between nodes on a packet-switched network. The protocol analyzer passively monitors the network and measures network traffic in accordance with a user selected time interval (i.e., one second through four hours). The matrix display shows the network traffic via a grid having markers indicating the volume of traffic between two specific nodes (i.e., the first thirty-one nodes are individually specified and a single grid location is reserved for remaining nodes in the network in excess of thirty one), or the magnitude of traffic between one specific node and each of the other nodes. The protocol analyzer utilizes counters to maintain the amount of frames transmitted between nodes during a user-specified interval.
Further, U.S. Pat. No. 5,251,152 (Notess) discloses a system for collecting and displaying statistical data for a plurality of local area networks (LAN) wherein several remote nodes attached to a LAN collect and analyze LAN data (i.e., traffic) to produce statistics relating to the data. The statistics are sent to a management node for storage in a history file. The history file is periodically compressed to maintain the history file size at a manageable level. The remote nodes employ various counters to produce the data statistics relating to network and packet characteristics, while the management node utilizes the statistics for various displays to show the network information. For example, the management node includes a traffic distribution display wherein vertical bars illustrate percentages of packets within a particular time interval having certain packet lengths.
U.S. Pat. No. 5,446,874 (Waclawsky et al) discloses a system for maintaining a standard of operation for a data communications network. The system initially monitors the network for a certain duration to generate benchmark data sets that contain the standard of operation for the network. The benchmark data sets are typically categorized by traffic type or activity (e.g., batch, interactive, voice, etc.). Current network activity is measured by the system and compared to the benchmark data sets via criteria modules that interface to an expert system. When the network activity is determined to be beyond normal behavior, the criteria modules notify the expert system such that the expert system may modify network routing, close applications or allocate additional bandwidth. In addition, the benchmark data sets may be modified or updated to include a recent representation of network behavior.
The prior art suffers from several disadvantages. Typically, probes utilized for monitoring communications system activity have limited resources and memory. Since communications system traffic bursts (i.e., peaks or surges in system traffic) endure for short periods of time, the probe must collect information from the system at short sampling intervals to properly monitor traffic burst activity. However, monitoring the communications system with short sampling intervals for extended periods of time generates a large sample base that may exceed the probe's memory. For example, a probe with a one second sampling interval monitoring a communications system for fifteen minutes accumulates nine-hundred measurements. Although Notess (U.S. Pat. No. 5,251,152) utilizes file compression to maintain file size, the compressed file may still grow to exceed the probe's memory capacity, while the additional processing to compress and read the compressed file degrades performance. Further, incorporating additional processing and memory resources into the probes to accommodate large sample bases increases costs. Moreover, prior art devices generally display the amount or lengths of data traversing a communications system, thereby requiring the operator to determine system traffic and bandwidth utilization based on the data volume information. There is typically no provision to display the percentage of bandwidth utilized over a predetermined time interval in graphical form showing periods of high and low bandwidth utilization to enable an operator to quickly determine appropriate actions for adjusting the bandwidth to accommodate system behavior.